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WO2018179802A1 - Électrode négative pour batteries au lithium-ion et batterie au lithium-ion - Google Patents

Électrode négative pour batteries au lithium-ion et batterie au lithium-ion Download PDF

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Publication number
WO2018179802A1
WO2018179802A1 PCT/JP2018/003128 JP2018003128W WO2018179802A1 WO 2018179802 A1 WO2018179802 A1 WO 2018179802A1 JP 2018003128 W JP2018003128 W JP 2018003128W WO 2018179802 A1 WO2018179802 A1 WO 2018179802A1
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Prior art keywords
negative electrode
lithium ion
ion battery
active material
electrode active
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PCT/JP2018/003128
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English (en)
Japanese (ja)
Inventor
幸三 武田
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Ｎｅｃエナジーデバイス株式会社
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Application filed by Ｎｅｃエナジーデバイス株式会社 filed Critical Ｎｅｃエナジーデバイス株式会社
Priority to JP2019508655A priority Critical patent/JP6802904B2/ja
Priority to CN201880023360.XA priority patent/CN110476281B/zh
Priority to US16/497,911 priority patent/US20200099051A1/en
Publication of WO2018179802A1 publication Critical patent/WO2018179802A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode for a lithium ion battery and a lithium ion battery.
  • Laminated lithium ion batteries are used, for example, as power sources for electronic devices such as notebook computers and mobile phones, and as power sources for automobiles such as hybrid vehicles and electric vehicles.
  • a laminate-type lithium ion battery has a structure in which a power generation element composed of a positive electrode, an electrolyte, and a negative electrode is sealed with a laminate film.
  • a negative electrode used for a laminate-type lithium ion battery is mainly composed of a negative electrode active material layer and a current collector layer.
  • the negative electrode active material layer is obtained, for example, by applying and drying a negative electrode slurry containing a negative electrode active material, an aqueous binder resin, a thickener, a conductive aid, etc. on the surface of a current collector layer such as a metal foil. .
  • Patent Document 1 Japanese Patent Laid-Open No. 10-012411 discloses a graphite-carbon composite material comprising a core of graphite particles having an average particle diameter of 50 ⁇ m or less and a carbon layer covering the surface of the graphite particles by a chemical vapor deposition method.
  • a negative electrode material for a lithium ion secondary battery is disclosed, wherein the specific surface area of the graphite-carbon composite material is 1 m 2 / g or less and the equilibrium adsorbed water content is 0.3 wt% or less. Has been.
  • Patent Document 1 discloses a graphite-carbon composite material obtained by using graphite particles having a large charge capacity as a core, and subjecting the surface of the graphite particles to chemical vapor deposition to coat the surface with pyrolytic carbon having a small specific surface area. Is described as having a large reversible discharge capacity because of its large charge amount and high initial discharge efficiency.
  • Patent Document 2 Japanese Patent Laid-Open No. 11-2041059 discloses a graphite having an average particle diameter of 1 to 50 ⁇ m in a method for producing a negative electrode material for a lithium ion secondary battery using a nonaqueous electrolyte and using a carbon material as a negative electrode material.
  • a method for producing a negative electrode material for a lithium ion secondary battery characterized in that a graphite-carbon composite material is formed by coating the surface of the graphite particle with a carbon layer by a chemical vapor deposition method using the particle as a nucleus.
  • Patent Document 2 describes that when a negative electrode material obtained by the above-described manufacturing method is used, decomposition of the electrolyte solvent can be suppressed and a high-capacity lithium ion secondary battery can be realized.
  • Patent Document 3 International Publication No. 2015/037367 has an electrode element in which a positive electrode and a negative electrode are opposed to each other, a non-aqueous electrolyte, and an exterior body that contains the electrode element and the non-aqueous electrolyte.
  • a non-aqueous electrolyte secondary battery is characterized in that a water content in the negative electrode is 50 ppm to 1000 ppm, and the non-aqueous electrolyte contains a cyclic sulfonate derivative having a specific structure as an additive.
  • Patent Document 3 describes that a non-aqueous electrolyte secondary battery having the above configuration is excellent in coulomb efficiency.
  • the conventional laminate-type lithium ion battery has a large amount of gas generation at the first charge, and the battery may swell after the first charge. If the battery swells, the battery may burst or stress may be applied to the welded portion of the outer package.
  • a laminate-type lithium ion battery performs an aging process in which the battery is left at a constant temperature after the initial charge, and performs a process of determining the quality of the battery.
  • the lithium ion battery with a small amount of gas generation at the time of the first charge is suppressed in swelling of the battery, but this time, the decrease in the discharge capacity after the aging treatment may increase. That is, it has been clarified that the aging efficiency may be lowered. That is, the present inventors have found that there is a trade-off relationship between suppression of battery swelling and improvement of aging efficiency in a conventional laminate type lithium ion battery.
  • the present invention has been made in view of the above circumstances, and provides a negative electrode for a lithium ion battery capable of realizing a laminated lithium ion battery having good aging efficiency and suppressing battery swelling.
  • the present inventor has intensively studied to solve the above problems. As a result, it was found that by setting the water vapor adsorption amount of the negative electrode active material in a specific range, it is possible to suppress the swelling of the battery at the first charge while maintaining good aging efficiency, and completed the present invention. .
  • a negative electrode for a lithium ion battery comprising: Provided is a negative electrode for a lithium ion battery, wherein a water vapor saturated adsorption amount of the negative electrode active material layer measured by the following method is 0.03 cm 3 (STP) / g or more and 0.25 cm 3 (STP) / g or less. . (Method)
  • the negative electrode active material layer (3.0 g) is dried at 220 ° C. for 2 hours in a nitrogen atmosphere. Next, water vapor is adsorbed to the dried negative electrode active material layer at 25 ° C. by a constant volume method, and the water vapor saturated adsorption amount of the negative electrode active material layer is calculated.
  • a lithium ion battery comprising the above negative electrode for a lithium ion battery is provided.
  • a negative electrode for a lithium ion battery capable of realizing a laminate type lithium ion battery having good aging efficiency and suppressing battery swelling.
  • FIG. 1 is a cross-sectional view showing an example of the structure of a negative electrode 100 for a lithium ion battery according to an embodiment of the present invention.
  • the negative electrode 100 for a lithium ion battery according to this embodiment is provided on at least one surface of the current collector layer 101 and the current collector layer 101, and at least a part of the surface is amorphous carbon as a negative electrode active material And a negative electrode active material layer 103 containing a surface-coated graphite material coated with the above.
  • the water vapor saturation adsorption amount of the negative electrode active material layer 103 measured by the following method is 0.03 cm 3 (STP) / g or more and 0.25 cm 3 (STP) / g or less.
  • the negative electrode active material layer 103 (3.0 g) is dried at 220 ° C. for 2 hours in a nitrogen atmosphere. Next, water vapor is adsorbed to the dried negative electrode active material layer 103 at 25 ° C. by a constant volume method, and the water vapor saturation adsorption amount of the negative electrode active material layer 103 is calculated.
  • the water vapor saturated adsorption amount of the negative electrode active material layer 103 is more specifically measured by a constant volume method using a commercially available water vapor adsorption amount measuring device (for example, product name: BELSORP manufactured by Nippon Bell Co., Ltd.). be able to.
  • Cm 3 (STP) / g is the volume of water vapor that is saturated and adsorbed per negative electrode active material layer 103 (1 g), and represents the volume of water vapor in a standard state (0 ° C., 1 atm).
  • the conventional laminate-type lithium ion battery has a large amount of gas generation at the first charge, and the battery may swell after the first charge. If the battery swells, the battery may burst or stress may be applied to the welded portion of the outer package.
  • a laminate-type lithium ion battery performs an aging process in which the battery is left at a constant temperature after the initial charge, and performs a process of determining the quality of the battery.
  • the lithium ion battery with a small amount of gas generation at the time of the first charge is suppressed in swelling of the battery, but this time, the decrease in the discharge capacity after the aging treatment may increase.
  • the present inventors have found that there is a trade-off relationship between suppression of battery swelling and improvement of aging efficiency in a conventional laminate type lithium ion battery.
  • the present inventor has determined that the water vapor saturated adsorption amount of the negative electrode active material layer 103 measured by the above method is 0.03 cm 3 (STP) / g or more and 0.25 cm 3 (STP) / g or less. It was found that by making the range, the battery can be prevented from swelling during the first charge while maintaining good aging efficiency.
  • the upper limit of the water vapor saturation adsorption amount of the negative electrode active material layer 103 is 0.25 cm 3 (STP) / g or less, preferably 0.20 cm 3 (STP) / g or less, more preferably 0.16 cm 3 (STP). / G or less, particularly preferably 0.13 cm 3 (STP) / g or less.
  • the aging efficiency is improved while suppressing the swelling of the obtained lithium ion battery by setting the water vapor saturated adsorption amount of the negative electrode active material layer 103 to the upper limit value or less. be able to.
  • the lower limit of the water vapor saturation adsorption amount of the negative electrode active material layer 103 is 0.03 cm 3 (STP) / g or more, preferably 0.04 cm 3 (STP) / g or more, particularly preferably 0.05 cm 3 (STP). / G or more.
  • STP 0.03 cm 3
  • STP 0.04 cm 3
  • STP 0.05 cm 3
  • G G or more.
  • the negative electrode active material layer 103 having a water vapor saturated adsorption amount within the above range includes (A) a mixing ratio of the negative electrode active material layer 103 and (B) a surface-coated graphite material constituting the negative electrode active material layer 103. , Binder resin, thickener, type of conductive additive, (C) preparation method of negative electrode slurry for forming negative electrode active material layer 103, (D) drying method of negative electrode slurry, (E) negative electrode pressing method, etc. It can be realized by highly controlling the manufacturing conditions.
  • the coating amount of the amorphous carbon in the surface-coated graphite material, the firing temperature when coating the amorphous carbon on the graphite material, the mixing procedure of each component when preparing the negative electrode slurry examples include a drying method of the negative electrode slurry and a uniform pressure applied in the film thickness direction of the negative electrode active material layer 103.
  • the negative electrode active material layer 103 includes a negative electrode active material as an essential component, and further includes a binder resin, a thickener, and a conductive auxiliary as necessary.
  • the negative electrode active material included in the negative electrode active material layer 103 according to this embodiment includes a surface-coated graphite material in which at least a part of the surface is coated with amorphous carbon. That is, the surface-coated graphite material according to the present embodiment uses the graphite material as a core material, and at least a part of the surface of the graphite material is coated with amorphous carbon. In particular, the edge portion of the graphite material is preferably covered with the amorphous carbon.
  • the irreversible reaction between the edge part and the electrolyte can be suppressed, and as a result, the initial reduction in charge / discharge efficiency due to the increase in irreversible capacity can be further suppressed. can do.
  • examples of the amorphous carbon include soft carbon and hard carbon.
  • the graphite material used as the core material is not particularly limited as long as it is a normal graphite material that can be used for the negative electrode of a lithium ion battery.
  • artificial graphite produced by heat-treating natural graphite, petroleum-based, and coal-based coke can be used.
  • these graphite materials may be used alone or in combination of two or more.
  • natural graphite is preferable from the viewpoint of cost.
  • natural graphite refers to graphite that is naturally produced as ore.
  • Artificial graphite refers to graphite produced by an artificial technique and graphite close to perfect crystals of graphite. Such artificial graphite can be obtained, for example, by using a tar or coke obtained from coal residue, crude oil distillation residue, or the like as a raw material, followed by a firing step and a graphitization step.
  • the surface-coated graphite material according to the present embodiment is obtained by mixing the above-mentioned graphite material with an organic compound that is carbonized by a firing process and becomes amorphous carbon having lower crystallinity than the above-mentioned graphite material. It can be produced by calcinating an organic compound.
  • the organic compound to be mixed with the graphite material is not particularly limited as long as it is carbonized by firing to obtain amorphous carbon having lower crystallinity than the graphite material.
  • petroleum tar Tars such as coal-based tar
  • pitches such as petroleum-based pitch and coal-based pitch
  • thermoplastic resins such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile
  • phenol resin furfuryl alcohol
  • thermosetting resins such as resins
  • natural resins such as cellulose
  • aromatic hydrocarbons such as naphthalene, alkylnaphthalene, and anthracene.
  • these organic compounds may be used individually by 1 type, and may be used in combination of 2 or more type. Further, these organic compounds may be used by dissolving or dispersing in a solvent as necessary. Among the above organic compounds, tar and pitch are preferable from the viewpoint of price.
  • the specific surface area by the nitrogen adsorption BET method of the surface-coated graphite material according to the present embodiment is preferably 1.0 m 2 / g or more and 6.0 m 2 / g or less, more preferably 2.0 m 2 / g or more and 5 or less. 0.0 m 2 / g or less.
  • the specific surface area By setting the specific surface area to be equal to or greater than the above lower limit, the area for inserting and extracting lithium ions is increased, and the rate characteristics can be improved. Moreover, the binding property of binder resin can be improved by making a specific surface area into the said range.
  • the true specific gravity of the surface-coated graphite material according to the present embodiment is preferably 2.00 g / cm 3 or more and 2.50 g / cm 3 or less from the viewpoint of improving the battery characteristics of the obtained lithium ion battery. more preferably not more than 2.10 g / cm 3 or more 2.30 g / cm 3.
  • the amount of carbon dioxide gas adsorbed on the surface-coated graphite material according to this embodiment is preferably 0.05 ml / g or more and 1.0 ml / g or less from the viewpoint of improving the battery characteristics of the obtained lithium ion battery. Preferably they are 0.1 ml / g or more and 0.5 ml / g or less.
  • the coating amount of the amorphous carbon calculated by thermogravimetric analysis is preferably 0.5% by mass or more when the surface-coated graphite material is 100% by mass. 10.0% by mass or less, more preferably 0.7% by mass or more and 8.0% by mass or less, further preferably 0.7% by mass or more and 7.0% by mass or less, and particularly preferably 0.8% by mass or more. 6.5% by mass or less.
  • the coating amount of amorphous carbon By making the coating amount of amorphous carbon equal to or more than the above lower limit value, it is possible to suppress a decrease in initial charge / discharge efficiency due to an increase in irreversible capacity. Moreover, the stability of the negative electrode slurry mentioned later can be improved by making the coating amount of amorphous carbon more than the said lower limit.
  • the coating amount of amorphous carbon can be calculated by thermogravimetric analysis. More specifically, when the temperature of the surface-coated graphite material is increased to 900 ° C. at a temperature increase rate of 5 ° C./min in an oxygen atmosphere using a thermogravimetric analyzer (for example, TGA7 analyzer manufactured by Perkin Elma). The reduced mass from the temperature at which mass reduction starts to the temperature at which the mass reduction rate becomes gradual and then the mass reduction accelerates can be used as the coating amount.
  • a thermogravimetric analyzer for example, TGA7 analyzer manufactured by Perkin Elma
  • the average thickness of the coating layer made of amorphous carbon is preferably 0.5 nm or more and 100 nm or less, more preferably 1 nm or more and 80 nm or less, and further preferably It is 2 nm or more and 50 nm or less.
  • the average thickness of the coating layer made of amorphous carbon can be measured, for example, by taking a transmission electron microscope (TEM) image and using a caliper.
  • the surface-coated graphite material according to this embodiment can be produced, for example, by the following steps (1) to (4).
  • (1) The graphite material and the organic compound are mixed together with a solvent using a mixer or the like as necessary. By doing so, the organic compound is adhered to at least a part of the surface of the graphite material.
  • (2) When a solvent is used the obtained mixture is heated with stirring as necessary to remove the solvent.
  • (3) The mixture is heated in an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, argon gas or the like in a non-oxidizing atmosphere to carbonize the deposited organic compound. Then, a surface-coated graphite material in which at least a part of the surface of the graphite material is coated with amorphous carbon having lower crystallinity than the graphite powder is obtained.
  • the lower limit temperature of the heat treatment in this step is not particularly limited because it is appropriately determined depending on the type of organic compound, the coating amount, the heat history, etc., but is preferably 930 ° C. or higher, more preferably 950 ° C. or higher, more preferably 980 ° C. That's it.
  • the temperature of the heat treatment is preferably 930 ° C. or higher, more preferably 950 ° C. or higher, more preferably 980 ° C. That's it.
  • the upper limit temperature of the heat treatment in this step is not particularly limited because it is appropriately determined depending on the type of organic compound, the coating amount, the heat history, etc., but is preferably 1150 ° C. or less, more preferably 1100 ° C. or less, and still more preferably It is 1080 degrees C or less.
  • the temperature of the heat treatment By adjusting the temperature of the heat treatment to the upper limit value or less, the amount of water vapor adsorbed on the negative electrode active material can be improved. As a result, the water vapor saturation adsorption amount of the negative electrode active material layer 103 can be improved.
  • the heating rate, cooling rate, heat treatment time, and the like are also appropriately determined depending on the type of organic compound and the thermal history.
  • the coating layer may be oxidized after the coating treatment of the graphite material with the organic compound and before the coating layer is carbonized. By oxidizing the coating layer, high crystallization of the coating layer can be suppressed.
  • the obtained surface-coated graphite material is adjusted to a surface-coated graphite material having desired physical properties by performing pulverization, pulverization, classification treatment, and the like as necessary.
  • This step may be performed before the step (3), or may be performed both before and after the step (3). Moreover, you may perform a grinding
  • the method for producing the surface-coated graphite material of the present embodiment is not limited to the above method, and the surface-coated graphite material of the present embodiment can be obtained by appropriately adjusting various conditions. .
  • the average particle diameter d 50 in the volume-based particle size distribution measured by the laser diffraction / scattering particle size distribution measurement method for the surface-coated graphite material is preferably 1 ⁇ m or more from the viewpoint of suppressing side reactions during charging / discharging and suppressing reduction in charging / discharging efficiency. 5 ⁇ m or more is more preferable, 10 ⁇ m or more is more preferable, 15 ⁇ m or more is particularly preferable, and 40 ⁇ m or less is preferable, 30 ⁇ m or less is more preferable, and 25 ⁇ m or less is preferable from the viewpoint of input / output characteristics and electrode production (such as electrode surface smoothness). The following are particularly preferred:
  • the content of the negative electrode active material is preferably 85 parts by mass or more and 99 parts by mass or less, and more preferably 90 parts by mass or more and 98 parts by mass or less when the entire negative electrode active material layer 103 is 100 parts by mass. Preferably, it is 93 parts by mass or more and 97.5 parts by mass or less.
  • the binder resin used for the negative electrode active material layer 103 according to the present embodiment has a role of binding the negative electrode active materials to each other and the negative electrode active material layer 103 and the current collector layer 101.
  • the binder resin of this embodiment is not particularly limited as long as it can be electrode-molded and has sufficient electrochemical stability.
  • the binder resin is dispersed in an aqueous medium and used. A so-called aqueous binder resin is preferred.
  • the aqueous binder resin included in the negative electrode active material layer 103 according to the present embodiment for example, a rubber-based binder resin or an acrylic-based binder resin can be used.
  • the aqueous binder resin refers to a resin that can be dispersed in water to form an aqueous emulsion solution.
  • the aqueous binder resin according to this embodiment is preferably formed of latex particles and dispersed in water to be used as an aqueous emulsion solution. That is, the aqueous binder resin contained in the negative electrode active material layer 103 according to the present embodiment is preferably formed of latex particles of an aqueous binder resin.
  • the aqueous binder resin can be contained in the negative electrode active material layer 103 without inhibiting the contact between the negative electrode active materials, between the conductive assistants, and between the negative electrode active material and the conductive assistant.
  • the water in which the aqueous binder resin is dispersed may be mixed with water such as alcohol and a highly hydrophilic solvent.
  • the rubber binder resin examples include styrene / butadiene copolymer rubber.
  • the acrylic binder resin for example, a polymer (homopolymer or acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, acrylate, or methacrylate unit (hereinafter referred to as “acryl unit”)). Copolymer) and the like.
  • the copolymer include a copolymer containing an acrylic unit and a styrene unit, and a copolymer containing an acrylic unit and a silicon unit.
  • These aqueous binder resins may be used alone or in combination of two or more.
  • styrene / butadiene copolymer rubber is particularly preferable from the viewpoints of excellent binding properties, affinity with an electrolytic solution, price, electrochemical stability, and the like.
  • Styrene-butadiene copolymer rubber is a copolymer mainly composed of styrene and 1,3-butadiene.
  • the main component means that in the styrene / butadiene copolymer rubber, the total content of the constituent units derived from styrene and the constituent units derived from 1,3-butadiene is the total polymerization unit of the styrene / butadiene copolymer rubber. This refers to the case of 50% by mass or more.
  • the mass ratio (St / BD) between the structural unit derived from styrene (hereinafter also referred to as St) and the structural unit derived from 1,3-butadiene (hereinafter also referred to as BD) is, for example, 10/90 to 90 / 10.
  • the styrene / butadiene copolymer rubber may be copolymerized with monomer components other than styrene and 1,3-butadiene.
  • monomer components other than styrene and 1,3-butadiene examples thereof include conjugated diene monomers, unsaturated carboxylic acid monomers, and other known monomers that can be copolymerized.
  • conjugated diene monomer examples include isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, piperylene and the like.
  • the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like.
  • the method for producing the styrene / butadiene copolymer rubber is not particularly limited, but it is preferably produced by an emulsion polymerization method.
  • the emulsion polymerization method When the emulsion polymerization method is used, latex particles containing styrene / butadiene copolymer rubber can be obtained.
  • a conventionally known method is used as the emulsion polymerization.
  • styrene, 1,3-butadiene, and the above-mentioned various copolymerizable monomer components are preferably prepared by emulsion polymerization in water with the addition of a polymerization initiator, preferably in the presence of an emulsifier. Can do.
  • the average particle diameter of the latex particles containing the styrene / butadiene copolymer rubber to be obtained is not particularly limited, but is preferably 50 nm to 500 nm, more preferably 70 nm to 250 nm, and further 80 nm to 200 nm. 90 nm or more and 150 nm or less are especially preferable.
  • the average particle size is within the above range, the balance of swelling, elution, binding and dispersibility of the particles of the aqueous binder resin with respect to the electrolytic solution is further improved.
  • the average particle diameter of the latex particle in this embodiment represents a volume average particle diameter, and can be measured by a dynamic light scattering method.
  • the average particle diameter of latex particles by the dynamic light scattering method can be measured as follows.
  • the latex particle dispersion is diluted with water 200 to 1000 times depending on the solid content.
  • About 5 ml of this diluted solution is injected into a cell of a measuring apparatus (for example, Nikkiso Microtrac particle size analyzer), and after inputting the solvent (water in this embodiment) and the refractive index condition of the polymer according to the sample, measurement is performed. Do it.
  • the peak of the obtained volume particle size distribution data is defined as the average particle size of the present embodiment.
  • the content of the binder resin is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, and 0.5 parts by mass or more and 5.0 parts by mass when the entire negative electrode active material layer 103 is 100 parts by mass. More preferably, it is 0.8 parts by mass or more and 4.0 parts by mass or less, and particularly preferably 1.0 part by mass or more and 3.0 parts by mass or less.
  • the content of the binder resin is within the above range, the balance of the coating property of the negative electrode slurry, the binding property of the binder resin, and the battery characteristics is further improved. Further, it is preferable that the content of the binder resin is not more than the above upper limit value because the ratio of the negative electrode active material is increased and the capacity per electrode mass is increased. It is preferable for the content of the binder resin to be not less than the above lower limit value because electrode peeling is suppressed.
  • the negative electrode active material layer 103 may further include a thickener.
  • the thickener is not particularly limited as long as it improves the coating properties of the electrode slurry for forming the negative electrode active material layer 103.
  • Cellulose polymers such as cellulose and carboxyethyl methyl cellulose, and ammonium salts and alkali metal salts thereof; polycarboxylic acid; polyethylene oxide; polyvinyl pyrrolidone; polyacrylic acid salt such as sodium polyacrylate; polyvinyl alcohol; Can be mentioned.
  • at least one selected from the group consisting of a cellulose polymer, an ammonium salt of a cellulose polymer, and an alkali metal salt of a cellulose polymer is preferable.
  • Carboxymethyl cellulose, an ammonium salt of carboxymethyl cellulose, and an alkali metal salt of carboxymethyl cellulose are preferred. More preferred.
  • These thickeners may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the content of the thickener is preferably 0.1 parts by weight or more and 5.0 parts by weight or less, and 0.3 parts by weight or more and 3.0 parts by weight or less when the entire negative electrode active material layer 103 is 100 parts by weight. More preferably, it is 0.5 parts by mass or less and even more preferably 2.0 parts by mass or less. When the use amount of the thickener is within the above range, the balance between the coating property of the negative electrode slurry and the binding property of the binder resin is further improved.
  • the conductive auxiliary agent contained in the negative electrode active material layer 103 according to the present embodiment is not particularly limited as long as it improves the conductivity of the electrode.
  • These conductive aids may be used alone or in combination of two or more.
  • the content of the conductive auxiliary agent is preferably 0.05 parts by mass or more and 5.0 parts by mass or less, and 0.08 parts by mass or more and 3.0 parts by mass or less when the entire negative electrode active material layer 103 is 100 parts by mass. More preferably, it is 0.1 part by mass or more, and further preferably 0.2 part by mass or more and 1.0 part by mass or less.
  • the content of the conductive assistant is within the above range, the balance of the coating property of the negative electrode slurry, the binding property of the binder resin, and the battery characteristics is further improved.
  • the content of the conductive assistant is not more than the above upper limit value because the ratio of the negative electrode active material increases and the capacity per electrode mass increases. It is preferable for the content of the conductive assistant to be equal to or higher than the lower limit because the conductivity of the negative electrode becomes better.
  • the content of the negative electrode active material is preferably 85 parts by mass or more and 99 parts by mass or less, more preferably 90 parts by mass. Part to 98 parts by mass, more preferably 93 parts to 97.5 parts by mass.
  • the content of the binder resin is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, more preferably 0.5 parts by mass or more and 5.0 parts by mass or less, and further preferably 0.8 parts by mass or more. 0 parts by mass or less, particularly preferably 1.0 parts by mass or more and 3.0 parts by mass or less.
  • the content of the thickener is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.3 parts by mass or more and 3.0 parts by mass or less, and further preferably 0.5 parts by mass or more and 2 parts by mass or less. 0.0 parts by mass or less.
  • the conductive auxiliary agent content is preferably 0.05 parts by mass or more and 5.0 parts by mass or less, more preferably 0.08 parts by mass or more and 3.0 parts by mass or less, and further preferably 0.1 parts by mass or more and 2 parts by mass or less. 0.0 part by mass or less, particularly preferably 0.2 part by mass or more and 1.0 part by mass or less.
  • the density of the negative electrode active material layer 103 from the viewpoint of further improving the energy density of the lithium obtained ion battery, preferably 1.30 g / cm 3 or more, 1.40 g / cm 3 or more is more preferable.
  • the upper limit of the density of the negative electrode active material layer 103 is not particularly limited, but is 1.90 g / cm 3 or less from the viewpoint of improving electrolyte penetration into the electrode and further suppressing lithium deposition on the electrode. preferable.
  • the density of the negative electrode active material layer 103 is calculated by calculating the mass per unit volume by measuring the mass and thickness of the negative electrode active material layer 103 having a predetermined size (for example, 5 cm ⁇ 5 cm). it can.
  • the thickness of the negative electrode active material layer 103 is not particularly limited, and can be appropriately set according to desired characteristics. For example, it can be set thick from the viewpoint of energy density, and can be set thin from the viewpoint of output characteristics.
  • the thickness of the negative electrode active material layer 103 can be appropriately set, for example, in the range of 50 to 1000 ⁇ m, preferably 100 to 800 ⁇ m, more preferably 120 to 500 ⁇ m.
  • the collector layer 101 Although it does not specifically limit as the collector layer 101 which concerns on this embodiment, copper, stainless steel, nickel, titanium, or these alloys can be used, price, availability, electrochemical stability, etc. From the viewpoint, copper is particularly preferable. Further, the shape of the current collector layer 101 is not particularly limited, but a foil shape, a flat plate shape, or a mesh shape is preferably used in a thickness range of 0.001 mm to 0.5 mm.
  • the manufacturing method of the negative electrode 100 for lithium ion batteries which concerns on this embodiment is demonstrated.
  • the method for manufacturing the negative electrode 100 for a lithium ion battery according to the present embodiment is different from the conventional method for manufacturing an electrode.
  • the blending ratio of the negative electrode active material layer 103 and the negative electrode active material layer 103 are configured.
  • the negative electrode 100 for a lithium ion battery according to this embodiment can be obtained for the first time by a manufacturing method that highly controls various factors relating to the following five conditions (A) to (E).
  • A Mixing ratio of negative electrode active material layer 103
  • B Types of surface-coated graphite material, binder resin, thickener and conductive additive constituting negative electrode active material layer 103
  • C Form negative electrode active material layer 103 For preparing negative electrode slurry
  • D Drying method for negative electrode slurry
  • E Pressing method for negative electrode
  • the negative electrode 100 for a lithium ion battery according to the present embodiment is based on specific control conditions such as kneading time and kneading temperature of the negative electrode slurry, on the premise that various factors related to the above five conditions are highly controlled.
  • Various types can be adopted.
  • the negative electrode 100 for a lithium ion battery according to the present embodiment can be manufactured by adopting a known method except for highly controlling the various factors related to the above five conditions. .
  • an example of a method for manufacturing the negative electrode 100 for a lithium ion battery according to the present embodiment will be described on the assumption that various factors related to the above five conditions are highly controlled.
  • the method for manufacturing the negative electrode 100 for a lithium ion battery preferably includes the following three steps (1) to (3).
  • the obtained negative electrode slurry is placed on the current collector layer 101
  • each step will be described. To do.
  • a negative electrode slurry is prepared by mixing a surface-coated graphite material, a binder resin, a thickener, and a conductive additive. Since the types and blending ratios of the negative electrode active material, the binder resin, the thickener, and the conductive auxiliary agent have been described above, the description thereof is omitted here.
  • the negative electrode slurry is obtained by, for example, dispersing or dissolving a surface-coated graphite material, a water-based binder resin, a thickener, and a conductive additive in a solvent such as water.
  • the mixing procedure for each component is dry mixing the surface-coated graphite material and the conductive additive, followed by wet mixing by adding a water-based binder resin emulsion aqueous solution and thickener solution, and if necessary, a solvent such as water. It is preferable to prepare a negative electrode slurry.
  • the dispersibility of the conductive auxiliary agent and the aqueous binder resin in the negative electrode active material layer 103 is improved, and the aqueous binder resin, the thickener and the conductive auxiliary agent are unevenly distributed on the surface of the negative electrode active material layer 103. It is possible to suppress the water vapor so that the water vapor can penetrate into the negative electrode active material layer 103. As a result, the water vapor saturation adsorption amount of the negative electrode active material layer 103 can be improved.
  • a known mixer such as a ball mill or a planetary mixer can be used as the mixer used, and is not particularly limited.
  • the negative electrode active material layer 103 is formed by applying the obtained negative electrode slurry onto the current collector layer 101 and drying it.
  • the negative electrode slurry obtained in the above step (1) is applied on the current collector layer 101 and dried, and the solvent is removed to form the negative electrode active material layer 103 on the current collector layer 101.
  • a generally known method can be used as the method for applying the negative electrode slurry onto the current collector layer 101.
  • a generally known method can be used. Examples thereof include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method.
  • the doctor blade method, the knife method, and the extrusion method are preferable in that a favorable surface state of the coating layer can be obtained in accordance with physical properties such as viscosity of the negative electrode slurry and drying properties.
  • the negative electrode slurry may be applied only on one side of the current collector layer 101 or on both sides. In the case of applying to both surfaces of the current collector layer 101, it may be applied sequentially on each side or on both sides simultaneously. Moreover, you may apply
  • the negative electrode slurry applied on the current collector layer 101 it is preferable to carry out slowly at a low temperature of about 40 to 80 ° C. over a long period of time. By doing so, it is possible to suppress the water-based binder resin, the thickener, and the conductive additive from being unevenly distributed on the surface of the negative electrode active material layer 103, and to improve the water penetration property of the negative electrode active material layer 103. be able to. As a result, the water vapor saturation adsorption amount of the negative electrode active material layer 103 can be improved.
  • the negative electrode active material layer 103 is formed, it is preferably dried at a high temperature of about 100 to 150 ° C. to remove moisture in the negative electrode active material layer 103.
  • the negative electrode active material layer 103 formed on the current collector layer 101 is pressed together with the current collector layer 101.
  • a roll press that can increase the linear pressure and can uniformly apply pressure in the film thickness direction of the negative electrode active material layer 103 is preferable. Accordingly, it is possible to suppress the density of the surface of the negative electrode active material layer 103 from being extremely higher than the density on the current collector layer 101 side, and to improve the water penetration property of the negative electrode active material layer 103. it can. As a result, the water vapor saturation adsorption amount of the negative electrode active material layer 103 can be improved.
  • FIG. 2 is a cross-sectional view showing an example of the structure of the lithium ion battery 80 according to the embodiment of the present invention.
  • the lithium ion battery 80 according to the present embodiment is a lithium ion secondary battery.
  • the lithium ion battery 80 according to this embodiment includes a negative electrode 100 for a lithium ion battery. For example, as shown in FIG.
  • a lithium ion battery 80 includes a positive electrode 1 having a positive electrode active material layer 2 and a positive electrode current collector 3, an electrolyte layer containing a separator 20 and an electrolyte, a negative electrode active
  • the positive electrode terminal 11 electrically connected to the positive electrode current collector 3 and at least partly exposed to the outside of the exterior body 30 and the negative electrode current collector 8, and at least partly And a negative electrode terminal 16 exposed outside the exterior body 30.
  • the negative electrode 6 contains the negative electrode 100 for lithium ion batteries which concerns on this embodiment.
  • the lithium ion battery 80 according to this embodiment can be manufactured according to a known method.
  • the form and type of the lithium ion battery 80 according to the present embodiment are not particularly limited, but can be configured as follows, for example.
  • FIG. 2 schematically shows an example of a configuration when the lithium ion battery 80 according to the present embodiment is a laminate type lithium ion battery.
  • a laminate-type lithium ion battery includes a battery body 50 including one or more power generation elements in which positive electrodes 1 and negative electrodes 6 are alternately stacked with separators 20 interposed therebetween. (Not shown) and is housed in a container made of the outer package 30.
  • a positive electrode terminal 11 and a negative electrode terminal 16 are electrically connected to the power generation element, and a part or all of the positive electrode terminal 11 and the negative electrode terminal 16 are drawn out of the exterior body 30.
  • the positive electrode 1 is provided with a positive electrode active material coating portion (positive electrode active material layer 2) and an uncoated portion on the front and back surfaces of the positive electrode current collector 3, and the negative electrode 6 is provided with front and back surfaces of the negative electrode current collector 8.
  • An application part (negative electrode active material layer 7) of the negative electrode active material and an unapplied part are provided.
  • An uncoated portion of the positive electrode active material in the positive electrode current collector 3 is used as a positive electrode tab 10 for connecting to the positive electrode terminal 11, and a negative electrode for connecting an uncoated portion of the negative electrode active material in the negative electrode current collector 8 to the negative electrode terminal 16.
  • This is tab 5.
  • the positive electrode tabs 10 are grouped together on the positive electrode terminal 11 and connected together with the positive electrode terminal 11 by ultrasonic welding or the like, and the negative electrode tabs 5 are grouped together on the negative electrode terminal 16 and connected together with the negative electrode terminal 16 through ultrasonic welding or the like Is done.
  • one end of the positive electrode terminal 11 is drawn out of the exterior body 30, and one end of the negative electrode terminal 16 is also drawn out of the exterior body 30.
  • An insulating member can be formed on the boundary portion 4 between the coated portion and the uncoated portion of the positive electrode active material as necessary.
  • the insulating member is not only the boundary portion 4 but also both the positive electrode tab and the positive electrode active material. It can be formed near the boundary.
  • an insulating member can be formed on the boundary portion 9 between the coated portion and the uncoated portion of the negative electrode active material as necessary, and can be formed near the boundary portion of both the negative electrode tab and the negative electrode active material.
  • the outer dimension of the negative electrode active material layer 7 is larger than the outer dimension of the positive electrode active material layer 2 and smaller than the outer dimension of the separator 20.
  • the positive electrode 1 is not particularly limited, and can be appropriately selected from positive electrodes that can be used for known lithium ion batteries depending on the application.
  • the positive electrode 1 includes a positive electrode active material layer 2 and a positive electrode current collector 3.
  • the positive electrode active material used for the positive electrode 1 is preferably a material having high electron conductivity so that lithium ions can be reversibly released and occluded and electron transport can be easily performed.
  • the positive electrode active material used for the positive electrode 1 include composite oxides of lithium and transition metals such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide. Transition metal sulfides such as TiS 2 , FeS, and MoS 2 ; transition metal oxides such as MnO, V 2 O 5 , V 6 O 13 , and TiO 2 , and olivine-type lithium phosphorus oxide.
  • the olivine-type lithium phosphorus oxide is, for example, at least one member selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe. It contains elements, lithium, phosphorus, and oxygen. In order to improve the characteristics of these compounds, some elements may be partially substituted with other elements.
  • olivine type lithium iron phosphorus oxide, lithium cobalt composite oxide, lithium nickel composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide are preferable.
  • These positive electrode active materials have a high working potential, a large capacity, and a large energy density.
  • a positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.
  • a binder resin, a conductive aid or the like can be added as appropriate to the positive electrode active material.
  • the conductive auxiliary agent carbon black, carbon fiber, graphite or the like can be used.
  • the binder resin polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose, modified acrylonitrile rubber particles, and the like can be used.
  • the positive electrode 1 is not particularly limited, but can be manufactured by a known method. For example, a method in which a positive electrode active material, a conductive additive, and a binder resin are dispersed in an organic solvent to obtain a slurry, and the slurry is applied to the positive electrode current collector 3 and then dried can be employed.
  • the thickness and density of the positive electrode 1 are not particularly limited because they are appropriately determined according to the intended use of the battery and the like, and can generally be set according to known information.
  • the positive electrode current collector 3 is not particularly limited, and those generally used for lithium ion batteries can be used, and examples thereof include aluminum, stainless steel, nickel, titanium, and alloys thereof. Aluminum is preferable as the positive electrode current collector 3 from the viewpoints of price, availability, electrochemical stability, and the like.
  • the negative electrode 6 includes the negative electrode 100 for a lithium ion battery according to this embodiment. Moreover, according to a use etc., you may further include the negative electrode which can be used for a well-known lithium ion battery. Hereinafter, the negative electrode 6 other than the negative electrode 100 for a lithium ion battery according to the present embodiment will be described.
  • the negative electrode 6 includes a negative electrode active material layer 7 and a negative electrode current collector 8.
  • the negative electrode active material used for the negative electrode 6 other than the negative electrode 100 for a lithium ion battery according to the present embodiment can be appropriately set depending on the use and the like as long as it can be used for the negative electrode.
  • Specific examples of materials that can be used as the negative electrode active material include carbon materials such as artificial graphite, natural graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn; lithium metal materials; silicon and tin An alloy-based material; an oxide-based material such as Nb 2 O 5 or TiO 2 ; or a composite thereof can be used.
  • a negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.
  • a binder resin, a conductive auxiliary agent, and the like can be appropriately added to the negative electrode active material, similarly to the positive electrode active material.
  • These binders and conductive agents can be the same as those added to the positive electrode active material.
  • the negative electrode current collector 8 copper, stainless steel, nickel, titanium or an alloy thereof can be used, and among these, copper is particularly preferable.
  • the negative electrode 6 in this embodiment can be manufactured by a well-known method. For example, after a negative electrode active material and a binder resin are dispersed in an organic solvent to obtain a slurry, a method of applying and drying the slurry on the negative electrode current collector 8 can be employed.
  • the electrolyte layer is a layer disposed so as to be interposed between the positive electrode 1 and the negative electrode 6.
  • the electrolyte layer includes the separator 20 and an electrolytic solution, and examples thereof include a porous separator impregnated with a nonaqueous electrolytic solution.
  • the separator 20 is not particularly limited as long as it has a function of electrically insulating the positive electrode 1 and the negative electrode 6 and transmitting lithium ions.
  • a porous separator can be used.
  • a porous resin film etc. are mentioned as a porous separator.
  • the resin constituting the porous resin film include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like.
  • a porous polyolefin film is preferable, and a porous polyethylene film and a porous polypropylene film are more preferable.
  • polypropylene resin which comprises a porous polypropylene film
  • the propylene homopolymer, the copolymer of a propylene and another olefin, etc. are mentioned, A propylene homopolymer (homopolypropylene) is preferable.
  • Polypropylene resins may be used alone or in combination of two or more.
  • the olefin copolymerized with propylene include ⁇ such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 1-decene. -Olefin and the like.
  • polyethylene-type resin which comprises a porous polyethylene film
  • ethylene homopolymer the copolymer of ethylene and another olefin, etc.
  • An ethylene homopolymer (homopolyethylene) is preferable.
  • Polyethylene resins may be used alone or in combination of two or more.
  • the olefin copolymerized with ethylene include ⁇ -olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 1-decene. Etc.
  • the thickness of the separator 20 is preferably 5 ⁇ m or more and 50 ⁇ m or less, more preferably 10 ⁇ m or more and 40 ⁇ m or less, from the viewpoint of the balance between mechanical strength and lithium ion conductivity.
  • the separator 20 preferably further includes a ceramic layer on at least one surface of the porous resin film from the viewpoint of further improving the heat resistance.
  • the separator 20 can further reduce thermal shrinkage and further prevent a short circuit between the electrodes.
  • the ceramic layer can be formed, for example, by applying a ceramic layer forming material on the porous resin layer and drying it.
  • a ceramic layer forming material for example, a material in which an inorganic filler and a binder resin are dissolved or dispersed in an appropriate solvent can be used.
  • the inorganic filler used for the ceramic layer can be appropriately selected from known materials used for lithium ion battery separators. For example, oxides, nitrides, sulfides, carbides, etc. with high insulating properties are preferable, and selected from oxide ceramics such as titanium oxide, alumina, silica, magnesia, zirconia, zinc oxide, iron oxide, ceria, yttria, etc. More preferably, one or two or more inorganic compounds prepared in the form of particles. Among these, titanium oxide and alumina are preferable.
  • the binder resin is not particularly limited, and examples thereof include cellulose resins such as carboxymethyl cellulose (CMC); acrylic resins; fluorine resins such as polyvinylidene fluoride (PVDF); Binder resin may be used individually by 1 type, and may be used in combination of 2 or more type.
  • CMC carboxymethyl cellulose
  • PVDF polyvinylidene fluoride
  • the solvent for dissolving or dispersing these components is not particularly limited, and is appropriately selected from, for example, water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. Can be used.
  • alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like.
  • NMP N-methylpyrrolidone
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • the thickness of the ceramic layer is preferably 1 ⁇ m or more and 20 ⁇ m or less, more preferably 1 ⁇ m or more and 12 ⁇ m or less, from the viewpoint of the balance of mechanical strength, handleability, and lithium ion conductivity.
  • the electrolytic solution according to this embodiment is obtained by dissolving an electrolyte in a solvent.
  • the electrolyte include lithium salts, which may be selected according to the type of active material.
  • Examples include SO 3 Li, CH 3 SO 3 Li, LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 2 N, and a lower fatty acid lithium carboxylate.
  • the solvent for dissolving the electrolyte is not particularly limited as long as it is usually used as a liquid for dissolving the electrolyte.
  • a known member can be used for the outer package 30 according to the present embodiment, and a laminate film having a metal layer and a heat-fusible resin layer is preferably used from the viewpoint of reducing the weight of the battery.
  • a metal layer a metal layer having a barrier property such as preventing leakage of the electrolytic solution or intrusion of moisture from the outside can be selected.
  • stainless steel (SUS), aluminum, copper, or the like can be used.
  • the resin material constituting the heat-fusible resin layer is not particularly limited, and for example, polyethylene, polypropylene, nylon, polyethylene terephthalate (PET), or the like can be used.
  • the heat sealable resin layers of the laminate film are opposed to each other via the battery main body 50, and the exterior body 30 is formed by heat-sealing the periphery of the portion that houses the battery main body 50. it can.
  • a resin layer such as a nylon film or a polyester film can be provided on the surface of the exterior body that is the surface opposite to the surface on which the heat-fusible resin layer is formed.
  • Electrode terminal In the present embodiment, known members can be used for the positive electrode terminal 11 and the negative electrode terminal 16.
  • the positive electrode terminal 11 can be made of, for example, aluminum or an aluminum alloy
  • the negative electrode terminal 16 can be made of, for example, copper, a copper alloy, or nickel plated thereon.
  • Each terminal is pulled out to the outside of the container, and a heat-sealable resin can be provided in advance at a position of each terminal located at a portion where the periphery of the outer package 30 is thermally welded.
  • the insulating member In the case where the insulating member is formed at the boundary portions 4 and 9 between the application portion and the non-application portion of the active material, polyimide, glass fiber, polyester, polypropylene, or those containing these in the configuration can be used.
  • the insulating member can be formed by applying heat to these members and fusing them to the boundaries 4 and 9 or by applying a gel-like resin to the boundaries 4 and 9 and drying.
  • the surface-coated graphite materials 1 to 6 were produced as follows.
  • the average particle size d 50 is manufactured by Microtrac, it was measured by MT3000 device, specific surface area, Quantachrome Corporation, Inc., using a Quanta Sorb, determined by nitrogen adsorption BET method.
  • the coating amount of the amorphous carbon was increased to 900 ° C. using a thermogravimetric analyzer (TGA7 analyzer manufactured by Perkin Elma Co., Ltd.) in an oxygen atmosphere at a heating rate of 5 ° C./min.
  • TGA7 analyzer manufactured by Perkin Elma Co., Ltd.
  • the amount of carbon dioxide adsorbed was measured by a constant volume method using NOVA2000 manufactured by QUANTACHROM, using 3 g of surface-coated graphite material dried at 220 ° C. for 2 hours in a nitrogen atmosphere.
  • the adsorption amount is a value converted to a standard state (STP).
  • STP standard state
  • the negative electrode was produced as follows.
  • the surface-coated graphite material 1 was used. Latex particles made of styrene / butadiene copolymer rubber were used as an aqueous binder resin, carboxymethyl cellulose was used as a thickener, and carbon black (average particle diameter d 50 : 100 nm) was used as a conductive assistant.
  • the surface-coated graphite material 1 as the negative electrode active material and the conductive auxiliary were dry mixed.
  • a negative electrode slurry was prepared by adding a thickener aqueous solution, an aqueous aqueous emulsion of a water-based binder resin, and water to the resulting mixture, followed by wet mixing.
  • This negative electrode slurry was applied to both surfaces of a copper foil as a negative electrode current collector and dried to prepare a negative electrode.
  • drying of the negative electrode slurry was performed by heating at 50 ° C. for 15 minutes. By this drying, a negative electrode active material layer was formed on the copper foil.
  • heat treatment was performed at 110 ° C. for 10 minutes to completely remove moisture in the negative electrode.
  • the copper foil and the negative electrode active material layer were pressed by a roll press, and a negative electrode having a negative electrode active material layer density of 1.46 g / cm 3 (the coating amount of the negative electrode active material layer per side: 9 mg / cm 2 ) Obtained.
  • a mixed oxide (positive electrode active material) obtained by mixing LiMn 2 O 4 and LiNi 0.85 Co 0.15 O 2 at a mass ratio of 78:22 as a positive electrode active material, carbon black as a conductive additive, and polyvinylidene fluoride as a binder resin was used. These were dispersed or dissolved in N-methyl-pyrrolidone (NMP) to prepare a positive electrode slurry. This positive electrode slurry was applied to an aluminum foil as a positive electrode current collector and dried. Subsequently, the aluminum foil and the positive electrode active material layer were pressed by a roll press to obtain a positive electrode having a positive electrode active material layer density of 3.0 g / cm 3 .
  • NMP N-methyl-pyrrolidone
  • Water vapor saturated adsorption amount [cm 3 (STP) / g] (total water vapor introduction amount ⁇ water vapor amount required to make relative pressure (P / P 0 ) 0.1) / mass of negative electrode active material layer
  • the water vapor saturated adsorption amount is a value converted into a standard state (STP).
  • Table 2 shows the above evaluation results.
  • Example 2 to 4 and Comparative Examples 1 to 2 A negative electrode and a lithium ion battery were prepared and evaluated in the same manner as in Example 1 except that the surface-coated graphite material 1 was changed to the surface-coated graphite materials 2 to 6 shown in Table 1. Each evaluation result is shown in Table 2.
  • the lithium ion battery of the Example using the negative electrode whose water vapor saturated adsorption amount of the negative electrode active material layer is 0.03 cm 3 (STP) / g or more and 0.25 cm 3 (STP) / g or less has an aging efficiency. It was good and the gas generation amount was suppressed.
  • the lithium ion battery of Comparative Example 1 using a negative electrode in which the water vapor saturation adsorption amount of the negative electrode active material layer exceeded 0.25 cm 3 (STP) / g was low and inferior in aging efficiency.
  • the lithium ion battery of Comparative Example 2 using a negative electrode having a water vapor saturation adsorption amount of less than 0.03 cm 3 (STP) / g of the negative electrode active material layer generates a large amount of gas and cannot suppress swelling of the battery. It was. From the above, by using a negative electrode in which the water vapor saturation adsorption amount of the negative electrode active material layer is 0.03 cm 3 (STP) / g or more and 0.25 cm 3 (STP) / g or less, aging efficiency is good, and the battery It can be understood that a laminate-type lithium ion battery with suppressed swelling can be realized.

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Abstract

Le but de la présente invention est de fournir une électrode négative pour batteries au lithium-ion, qui permet l'obtention d'une batterie au lithium-ion stratifiée qui a un bon rendement en vieillissement, tout en étant supprimée dans le gonflement de la batterie. Une électrode négative (100) pour des batteries au lithium-ion selon la présente invention comprend une couche collectrice (101) et une couche de matériau actif d'électrode négative (103) qui est disposée sur au moins une surface de la couche collectrice (101) et contient, en tant que matériau actif d'électrode négative, un matériau de graphite revêtu en surface, dont au moins une partie de la surface est revêtue d'un carbone amorphe. L'adsorption saturée en vapeur d'eau de la couche de matériau actif d'électrode négative (103) telle que déterminée par un procédé décrit ci-dessous est de 0,03 cm3 (STP)/g à 0,25 cm3 (STP)/g (inclus). (procédé) la couche de matériau actif d'électrode négative (103) (3,0 g) est séchée pendant 2 heures dans une atmosphère d'azote à 220 °C par la suite, la couche de matériau actif d'électrode négative séchée (103) est amenée à adsorber la vapeur d'eau à 25 °C au moyen d'un procédé à volume constant, ce qui permet de calculer l'adsorption saturée en vapeur d'eau de la couche de matériau actif d'électrode négative (103).
PCT/JP2018/003128 2017-03-31 2018-01-31 Électrode négative pour batteries au lithium-ion et batterie au lithium-ion WO2018179802A1 (fr)

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JP2019508655A JP6802904B2 (ja) 2017-03-31 2018-01-31 リチウムイオン電池用負極およびリチウムイオン電池
CN201880023360.XA CN110476281B (zh) 2017-03-31 2018-01-31 锂离子电池用负极和锂离子电池
US16/497,911 US20200099051A1 (en) 2017-03-31 2018-01-31 Negative electrode for lithium ion battery and lithium ion battery

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JP2017069661 2017-03-31

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